Variable volume pumping apparatus



Dec. 15, 1964 c. A. CLARK 3,161,136

VARIABLE VOLUME PUMPING APPARATUS Filed July 29, 1965 2 Sheets-Sheet l IN VEN TOR. C/aude ,4. 6/0 n HGENT From F/uid Source CK Dec. 15, 1964 c. A. CLARK 3,161,136

VARIABLE VOLUME PUMPING APPARATUS Filed July 29, 1965 2 Sheets-Sheet 2 INVEN C/auoe 9. 6/0

United States Patent Office 3,151,135 Patented Dec. 15, 1964 3,161,136 VARIABLE VOLUME PUMPING APPARATUS Claude A. Clark, Houston, Tex., assignor to The Dow Chemical (Zompany, Midland, 1VIich., a corporation of Delaware Filed July 29, 1963, Ser. No. 298,034 12 Claims. ((11. 103-38) This invention relates to pumps and particularly to reciprocating piston pumps which are capable of delivering varying volumes of fluid while the piston or pistons of the pump reciprocate at a substantially constant number of strokes per unit of time.

Other so-called variable volume pumps have been known for many years for specific uses, but for one reason or another these pumps are not well adapted for use in mobile service, such as oil and gas well treating service, for example. Such service requires maximum utilization of available horsepower to thereby deliver the maximum volume of pumped fluid against whatever pressure may develop without exceeding the strength limits of the equipment. Such' requirements necessitate minimum weight and bulk consistent with the achieving of other requirements, and ease and reliability in controlling the variable volume feature of the pump while under load. Exceptional reliability is necessary because the pump will be used often in remote areas where facilities are not available for making major repairs and because in well treating service equipment breakdown can result in great damage to the well under treatment. For example, a pump breakdown during a well cementing job could result in the cement setting up in the well casing before displacement can be eifected between the casing and well bore wall.

In conventional Well treating pumping units, a power source or prime mover, usually an internal combustion engine, transmission (which may include a torque converter) and the pump are disposed on a truck.

Any reduction in weight which can be achieved in the coupling of power to the pump of the treating unit would, obviously, permit the construction of a lighter treating unit or would permit the construction of a treating unit having an increased pumping capacity (either in volume or pressure, or both) without exceeding maximum gross weight requirements.

Accordingly, a principal object of this invention is to provide an improved variable volume pumping apparatus which is suitable for use in treating earth wells.

Another object of this invention is to provide an improved variable volume pumping apparatus which is compact in size with respect to its pumping capacity and power utilization over a wide range of pumping pressures.

A further object of this invention is to provide an improved mobile fluid pumping system for well treating service or the like.

In accordance with this invention a piston type positive displacement pump achieves an infinitely variable stroke between maximum and minimum limits through a controlled variable phase relationship between two mechanically interlocked crankshafts. These crankshafts operate through connecting rods to an equal-legged walking beam pinned at its centerline to a plunger crosshead. Similar planetary gears arev used to drive the crankshafts. Multiple disc clutches, one coupled between the frame of the pump and the planet carrier of each set of planetary gears, are used to establish and maintain the desired phase relationship between the crankshafts during operation. By slightly releasing one clutch to permit rotation of the planet carrier to which it is coupled by a predetermined amount, the phasing of the planetary gears coupled to each crankshaft may be changed with' respect toeach other. The phase relationship between crankshafts and hence the piston stroke may be changed inversely with the discharge pressure to provide a hydraulic horsepower output desirably matched to the available horsepower of the prime mover.

The invention, as well as additional objects and advantages thereof, will best be understood when the following detailed description is read in connection with the accompanying drawing, in which FIG. 1 is a simplified plan view, partly broken away and in section, of apparatus in accordance with this in vention;

FIG. 2 is a sectional view taken along the line 22 of FIG. 1;

FIG. 3 is a sectional view taken along the line 3--3 of FIG. 1;

FIG. 4 is a fragmentary end view of the drive gears of the apparatus showing chain drive coupling between the drive gears;

FIG. 5 is a side elevational view, in section, of a multiple disc clutch as used in FIG. 1; I

FIG. 6 is a sectional view taken along the line 6-6 of FIG. 5; and

FIG. 7 is a sectional view taken along the line 77 of FIG. 5.

Referring to the drawing, there is shown variable volume pump-ing apparatus, indicated generally by the numeral 10 mounted on a common frame shown. only in fragments. The apparatus includes a single action reciprocating piston-type pump 12 (see FIG. 3 especially) whose piston 14 is coupled to a crosshead plunger 15" adapted to reciprocate in the guide 15a, and to the center of an equal-legged walking beam 16 which in turn is coupled at its ends by connecting rods 18, 20 to crankshafts 22, 24, respectively, which are journaled in bearings 19, 21 and 19a, 21a, for example.

Each of the crankshafts 22, 24 has an end 23, 25 which is rigidly mechanically coupled to the ring gear 26, 28 of a planetary gear assembly 30, 32, respectively. The planetary gear assembly 30, shown in section in FIG. 2', is the same as the assembly 32 which is shown in plan in FIG. 1.

Spur gear wheels 78, 80 are rigidly coupled in a fixed rotational relationship to the shafts 36, 38, respectively, near the end of the shafts 36, 38 which is remote from the planetary gear assemblies 26, 28. The gears 78, 80 are of equal diameter and have an equal number of teeth, the teeth of one wheel engaging those of the other. Means, such as the gears, 82, 84 are coupled to the end of the shaft 36 whereby power from a prime mover 86 is coupled to the shaft 36 and thence through the spur wheels 78, 80 to the shaft 38. The power source 86', which may be an internal combustion engine or a gas turbine, or any suitable motor or engine, for example, is diagrammatically indicated by the block 86 and is coupled, as indicated by the shaft 87, to the gear 84. Bearings 64', 64a are provided near the ends of the drive shafts 36, 38 which are remote from the planetary gears 26, 28, respectively.

Each of the bearings 19, 19a, 21, 21a, 40,- 400, 64, 64a, clutch assemblies 60, 62, the pump 12 and guide 15a are mounted on common framework for the apparatus, which framework also carries the power source 86, the/framework being attached to or supported by the mobile unit, e.g. a truck, which carries the apparatus.

Referring now to, FIGS. 5, 6 and 7,.as well as to FIG. 1, the structure of the multiple disc clutch (perhapsv more accurately called a brake in view of its use) is shown in detail.

The section 102, adjacent disposed around a central tube 108 through which the drive shaft 36 (or 38) passes. A piston return spring 110, disposed between an outwardly extending flange 112 of the tube 108 and the piston 106, forces the piston 106 towards the end 114 of the section adjacent to the frame 63 except when the piston is forced forward by fluid, usually oil, pumped into the bore 104 into which the piston fits. Oil is pumped into and released from the bore by means of the line 92 which is also coupled to the clutch controller.

The second functional part of the section, 116, which extends beyond the bore 104, has splines 118 on its inner wall surface and an inwardly extending flange 120 at its end which is remote from the frame section 63. A plurality of discs 122 are fitted on and carried by the hollow splined part of the space between the piston 106 and the inwardly extending flange 120.

A hollow tube 124, having longitudinally extending splines 126 onto its outer surface, is telescoped within the outer housing and frame part 100 from the end thereof having the inwardly extending flange 120. The tube 124, as previously mentioned, is rigidly coupled to the planet carrier 59 (or 61) by means of its flange 128.

A plurality of discs 130 are fitted over and carried by the tube 124. The discs 122 and 130 are interleaved with one another, almost filling the space between the flange 120 and the forward end of the piston 106 when the piston is in its retracted position.

in operation, let it be assumed that the planet carriers 59, 61 are initially radially aligned with respect to one another. This can be determined by noting that the markers 134, 136 on the planet carrier discs 59, 61 are in the same relative position. The markers may be painted, cut, or etched onto the carriers 59, 61 if the checking of their relative positions is to be determined visually (usually using a stroboscopic light source in so doing). Alternatively, magnetic or radioactive markers may be used and their positions noted during operation of the pump by suitable detectors which are generally well known in the art.

In this above described position, the throws of the crankshafts 22, 24 are connected in an in-phase rotational relationship, and move the piston 14 of the pump 12 backwards and forward in the pump cylinder 88 at maximum stroke length as power from the gear 84 is coupled by means of the gear 82 to the shaft 36 and, by means of the spur gears 78, 80, to the shaft 33.

The shafts 36, 38 drive the sun gear (34 in FIG. 2) of each planetary gear assembly 30, 32, respectively. The sun gear of each assembly is coupled to the ring gear of its assembly 30, 32 through the planetary gears (46, 48 in FIG. 2) of the respective assembly 30 or 32. The planetary gears of the assembly are free to rotate on their shafts 50, 52 and 54, 56, but these pairs of shafts are held in a predetermined position with respect to eachother because oil, under pressure, is forced through the lines 92, 94, forcing the piston (106 in FIG. of each clutch to advance and placing the discs 122 and 130 in contact with each other (restrained by the flange 120) under sufiicient pressure to prevent any slippage of the discs and rotation of the tubular element 124 which is rigidly coupled to the planet carrier 59 (or 61). The shafts 50, 52 and 54, 56 are mounted in fixed position except when pressure driving the piston in one or both of the clutches 60, 62 is released enough to permit controlled slippage of the discs on the tubular element 124. The planetary gears are, however, free to rotate on their shafts 50, 52 (or 54, 56).

When the stroke length of the piston 14 is to be changed, the clutch controller 0 is operated to partially release, momentarily, the pressure on the piston 106 of one of the clutches 60, 62 to permit slippage of one clutch by a predetermined amount, thereby changing the phase relationship between the crankshafts 22, 24 as one planet carrier 59 or 61 changes its radial position (usually slowly) with respect to the other planet carrier. Such changing of position is usually at a slow rate as compared with the rate of rotation of the crankshafts 22, 24. The length of the piston stroke is at a maximum when the crankshafts 22, 24 are in phase as shown in FIG. 3 (rotating counter to one another). Piston stroke length decreases as the crankshafts become out of phase with respect to each other, that is, the length of the piston stroke is at a minimum when one of the connecting rods 18, 20 is at its most forward position with respect to the piston 14 and the other connecting rod is at its most rearward position with respect to the piston 14. Since both connecting rods 18, 20 are connected to the walking beam 16 which is coupled at its center to the crosshead 15, the movement of the piston 14 is a resultant of the movement of the two connecting rods 18, 20 and, when the connecting rods are in maximum out-of-phase relationship, is practically zero as to the walking beam pivots around its point of attachment to the crosshead.

When the phase relationship of the crankshafts is at an intermediate point between the in-phase relationship and the maximum out-of-phase relationship there will be some rocking of the walking beam about its point of attachment to the crosshead, and also some forward and backward motion of the piston 14.

It should be noted that in the apparatus thus far described, the rotation of the drive shafts 36, 38 has been in opposite radial direction because of the coupling together of the spur gears 78, 80.

The same changing in-phase relationship of the crankshaft throws also may be achieved with the clutches 60, 62 if the drive shafts 36, 38 are coupled, as by the spur gears 78a, 80a and chain drive 94 shown in FIG. 4, for example, to rotate in the same radial direction. The pressure on a piston of one of the clutches may be released sufficiently to permit controlled rotation of one (usually) of the planet carriers 59, 61, as previously described, thus changing the phase relationship between the crankshafts. The crankshafts 22, 24 may be brought into a closer inphase relationship by rotating either one of the planet carriers until the carriers are aligned to the required degree. Stated ditferently, if one planet carrier has been moved in relation to the other planet carrier to establish an out-of-phase relationship between the crank shafts, an in-phase relationship between the crankshafts may be accomplished by moving the earlier moved planet carrier until it is again aligned with the un-moved planet carrier. Alternatively, the previously un-moved planet carrier may itself be moved until it is aligned with the other planet carrier.

The apparatus described above provides means whereby, by changing the phase relationship between the crankshafts in appropriate amounts, constant horsepower may be applied to the pump 12 even though the pressure head against which the pump works may vary over a wide range. When the pressure head is low enough to permit such operation, keeping the two crankshafts operating on an in-phase relationship results in maximum volume being displaced through the pump 12. As the pressure head increases one of the clutches 60 or 62 is allowed to slip in a controlled manner to cause one of the crankshafts 22 or 24 to be moved in an increasingly out-of-phase relationship with respect to the other so that the available driving horsepower may be used to drive the piston 14 in increasingly shorter strokes and thus deliver less volume at a higher pressure.

Also, since the pump output can be continuously varied between practically no output and maximum output, there is no need for a torque converter or an additional speed varying transmission to be interposed between the power source and the pump apparatus providing the coupling between the power source 86 and the gear 82 does not cause the shafts 36, 38 to be rotated at excessive speeds.

.multiple cylinder pump, such as a quintiplex pump, for

example, may be coupled to suitable crankshafts which are substituted for the crankshafts 22, 24} arid which are driven by the ring gears 2d, 28.

The apparatus of the invention permits the power source to operate at a substantially constant r.p.m. rate even though the pumping rate varies widely. Thus, this apparatus is well adapted to be driven by turbinesor by an internal combustion piston-type engine operating at an optimum rpm. rate.

Because the pump is driven by two crankshafts, the bearing loading on the individual connecting rods is re duced. A single pump may deliver either a large volume at moderate pressures or smaller volume at high pressures. In fixed strokereciprocating piston-type pumps a so-called high volume pump has a relatively low maximum pumping'pressure in order to prevent overloading of the connecting rod bearings or to prevent the stalling of the prime mover. Conversely, a so-called high pressure fixed stroke piston pump is limited in the volume it can pump at lower pressures because of the safe r.p.m. rate of the crankshaft even though the connecting rod bearings may not be overloaded and the horsepower capabilities of the prime mover are not exceeded.

Pumping apparatus in accordance with this invention is move versatile than conventional apparatus in that it is good both as a high pressure-low volume pump and as a low pressure-high volume pump and it admits of continuous variation of the relationship between pressure or volume driving operation. Also, because no intermediate torque converter or speed varying transmission is used, the apparatus is more compact and lighter than a conventional unit of similar work capabilities.

An additional advantage of apparatus in accordance with this invention is that the multiple disc clutches 6b, 62 are light in weight yet can hold extreme loads without slippage. Such clutches, however, are easy to control, by suitably adjusting the pressure on the clutch actuating piston, to permit a controlled slow slippage to permit any desired movement of the planet carriers with respect to each other.

What is claimed is:

1. A mobile pumping unit comprising in combination a prime mover and a variable displacement pump, said pump comprising a frame, a cylinder and piston reciprocal therein, a crosshead, means for mechanically coupling the piston to the crosshead to reciprocate the piston with reciprocation of the crosshead, a walking beam having a central part and two end parts, said crosshead being pivotally coupled to said central part of said walking beam, a pair of crankshafts, each of said crankshafts having at least one throw, a pair of connecting rods, one of said connecting rods being pivotally coupled to one end part of said walking beam and to a throw on one of said pair of crankshafts', the other connecting rod being pivotally coupled to the other end of the walking beam and to a throw on said other crankshaft, a pair of planetary gear assemblies each comprising a sun gear, at least one planetary gear and a ring gear, said planetary gear being coupled to a rotatable planet carrier element, one of said crankshafts being operatively coupled to the ring gear of one of said planetary gear assemblies, the other of said pair of crankshafts being operatively coupled to the ring gear of the other of the planetary assemblies, a pair of drive shafts, means for coupling said prime mover to said drive shafts and for rotating each of said drive shafts at least approximately at the same rate, one of said drive shafts being operatively coupled to one of said sun gears, the other of said drive shafts being operatively coupled to the other of said sun gears, a pair of multiple disc clutches each having a fixed segment and a rotatable seg ment, the rotatable segment of each clutch being fixedly coupled to one of said planet carriers and the fixed segment of each clutch being rigidly coupled to said frame, and means for actuating said clutches independently of one another.

2-. A pumping unit in accordance with claim 1,;wherein said ,crankshafts are disposed parallel to one another. 7

3. A pumping unit in accordance with claim 1, wherein said drive shafts are disposed parallel with one another.

4. A pumping unit in accordance with claim 1, wherein the means for coupling the prime mover to the drive shafts includes means for rotating the drive shafts in opposite radial direction to one another.

5. A pumping unit in accordance with claim 1, wherein each drive shaft passes through one of said clutches.

6. A pumping unit in accordance with claim 5, wherein said means for actuating said clutches includes a hy draulic system coupled to a piston of each clutch.

7. A pumping'unit in accordance with claim 1, wherein said prime moveris coupled to said drive shaft through fixed-ratio gear means.

8. A pumping unit in accordance with claim 1, wherein said prime mover is a gas turbine.

9. A pumping unit in accordance with claim 1, wherein said prime mover is a reciprocating piston-type internal combustion engine.

10. A pumping unit in accordance with claim 1, wherein the sun gear, planetary gear and ring gear in one planetarygear assembly are the same as the corresponding part in the other planetary gear assembly.

11. A pumping unit in accordance with claim 1, wherein the longitudinal axis of the crank throw of each crankshaft is offset from the longitudinal axis of its crankshaft by an equal amount.

12. A pumping unit in accordance with claim 1, wherein the point of coupling of the crosshead to the walking beam is along a line perpendicular to and bisecting a line drawn between the points of coupling of the connecting rods to the walking beam.

No references cited. 

1. A MOBILE PUMPING UNIT COMPRISING IN COMBINATION A PRIME MOVER AND A VARIABLE DISPLACEMENT PUMP, SAID PUMP COMPRISING A FRAME, A CYLINDER AND PISTON RECIPROCAL THEREIN, A CROSSHEAD, MEANS FOR MECHANICALLY COUPLING THE PISTON TO THE CROSSHEAD TO RECIPROCATE THE PISTON WITH RECIPROCATION OF THE CROSSHEAD, A WALKING BEAM HAVING A CENTRAL PART AND TWO END PARTS, SAID CROSSHEAD BEING PIVOTALLY COUPLED TO SAID CENTRAL PART OF SAID WALKING BEAM, A PAIR OF CRANKSHAFTS, EACH OF SAID CRANKSHAFTS HAVING AT LEAST ONE THROW, A PAIR OF CONNECTING RODS, ONE OF SAID CONNECTING RODS BEING PIVOTALLY COUPLED TO ONE END PART OF SAID WALKING BEAM AND TO A THROW ON ONE OF SAID PAIR OF CRANKSHAFTS, THE OTHER CONNECTING ROD BEING PIVOTALLY COUPLED TO THE OTHER END OF THE WALKING BEAM AND TO A THROW ON SAID OTHER CRANKSHAFT, A PAIR OF PLANETARY GEAR ASSEMBLIES EACH COMPRISING A SUN GEAR, AT LEAST ONE PLANETARY GEAR AND A RING GEAR, SAID PLANETARY GEAR BEING COUPLED TO A ROTATABLE PLANET CARRIER ELEMENT, ONE OF SAID CRANKSHAFTS BEING OPERATIVELY COUPLED TO THE RING GEAR OF ONE OF SAID PLANETARY GEAR ASSEMBLIES, THE OTHER OF SAID PAIR OF CRANKSHAFTS BEING OPERATIVELY COUPLED TO THE RING GEAR OF THE OTHER OF THE PLANETARY ASSEMBLIES, A PAIR OF DRIVE SHAFTS, MEANS FOR COUPLING SAID PRIME MOVER TO SAID DRIVE SHAFTS AND FOR ROTATING EACH OF SAID DRIVE SHAFTS AT LEAST APPROXIMATELY AT THE SAME RATE, ONE OF SAID DRIVE SHAFTS BEING OPERATIVELY COUPLED TO ONE OF SAID SUN GEARS, THE OTHER OF SAID DRIVE SHAFTS BEING OPERATIVELY COUPLED TO THE OTHER OF SAID SUN GEARS, A PAIR OF MULTIPLE DISC CLUTCHES EACH HAVING A FIXED SEGMENT AND A ROTATABLE SEGMENT, THE ROTATABLE SEGMENT OF EACH CLUTCH BEING FIXEDLY COUPLED TO ONE OF SAID PLANET CARRIERS AND THE FIXED SEGMENT OF EACH CLUTCH BEING RIGIDLY COUPLED TO SAID FRAME, AND MEANS FOR ACTUATING SAID CLUTCHES INDEPENDENTLY OF ONE ANOTHER. 